I just finished baking this bread from The Bread Bible using the full starter development time (2 days). Even though I burned the top crust a bit, I have never in my life (68 years old) tasted rye bread as delicious as this. As the caraway seeds were new and fresh, the out-of-the-oven smell was almost overpowering. Upon cooling, it was perfect.
Thanks to Rose for all her careful research. This was a joy.
My second batch is in the fridge.

I made a sourdough rye starter. I had it a place that got too cold so I moved it into a warm space (180 deg F). It did not do much as Rose says for a couple of days. I could not bear to throw away the 1/2 I was supposed to discard upon the first refreshment so I used that to start a bread flour (white) starter-levain-barm. On the third day, it started to grow and by the fifth day, it went to the top of my Mason jar. So I refreshed them and after an hour stuck them in the fridge for the every three day refreshment. In two weeks, I’ll make a rye and a white sourdough bread. I am going for a quite sour bread, which I really like.

So finally, I would not fuss with grapes. There is plenty of something in the flour (rye) that makes the starter rise. I did use a tip from the Baker’s Apprentice (Peter Reinhart) to use unsweetened pineapple juice as the liquid for the first two days. It is supposed to eliminate harmful bacterial growth that spoils the batch.

And more finally than the last, this is really fun. I have baked so much bread lately, I have to give it away. Rose is a great teacher. Just do what she.says. All will go well.